Frost line depth in Mingo County, WV
How deep the ground freezes in Mingo County, WV
15 in. Dig to 15 in, just below the frost. Nearest NOAA station: Williamson, 7.2 mi.
Your building department sets the legal frost line depth (IRC Table R301.2(1)); footings must go below it (R403.1.4.1). Call them before you dig.